Access control systems are often installed within and around commercial, residential, or governmental buildings, for instance. Examples of these buildings include hospitals, warehouses, schools or universities, hotels, shopping malls, office buildings, and casinos. The access control systems are principally concerned with physical security and the selective restriction of or notification of access to a place or other resource. The access control systems typically include components such as access controllers, door lock controllers, and access control reader devices.
The access control reader devices work with access controllers to determine whether users are authorized to enter restricted areas. The access control reader devices are often installed throughout the buildings to control access to the restricted areas. Typically, users interact with the access control reader devices by swiping cards or bringing contactless keycards within range (approximately 2-3 inches or 5 centimeters) of the access control reader devices. The access control reader devices read identification information of the cards and then the access controllers determine if the users are authorized to enter the restricted areas. If the users are authorized to enter the restricted areas, then the access controllers might signal door lock controllers to unlock locked doors or open gates or signal elevator controllers to open the elevator doors or move to a new floor, for example.
Radio frequency identification (RFID) technology is commonly used in the contactless keycards. The cards have embedded RFID tags that are then read when they come into proximity with RFID readers. These RFID readers include two-way radio transmitter-receivers and use RFID antenna(s) that send signals to RFID tags and read their response. Generally, RFID tags are either passive, active, or battery-assisted passive. Active RFID tags periodically broadcast their identification signal whereas passive RFID tags are powered by RF energy transmitted from the reader. Finally, battery-assisted passive RFID tags transmit their identification signal when activated by the RFID reader.
Some access control reader devices also include numeric mechanical keypads. These keypads provide an alternative mechanism for interacting with the access control systems. In one example, after users swipe their cards or bring their contactless keycards within range, the users then enter personal identification numbers (PINs) using the numeric keypads. This provides an added level of security to handle situations in which access cards might have been lost or stolen. The access controllers then authorize users based on the entered PINs and the identification information from their cards.
For some applications, touch pads have replaced numeric mechanical keypads. The touch pads detect the users' touch often using a grid of monolithically-fabricated touch sensors. There are a number of touch sensor technologies, but the two most common are capacitive and resistive detection.
There are some advantages to replacing numeric keypads with touch pads. One advantage is that some touch pads require fewer parts than numeric keypads. Another advantage to replacing keypads with touch pads can be lowered manufacturing costs, reduced mechanical wear, and increased longevity.
Capacitive and resistive touch pads share a number of common components. They both have conductive touch sensors mounted or formed on a circuit board. A device controller then monitors those touch sensors to detect changes in capacitance or resistance as an indication of a user touching or coming into proximity with a particular sensor or the touch pad as a whole.